XML_Feed_Parser and Extensions

Description

Using XML namespaces, the various syndication formats are very
easy to extend and the number of extensions in use is enormous.

XML_Feed_Parser focuses on core functionality shared between the
various syndication formats. Some of the most common extensions are
handled natively—particularly when they provide one format with
features to bring it into line with others, such as the content
extension for RSS2—but the majority provide specialist content and
providing support for them would quickly result in a bloated package.

It is possible that a proper extensions mechanism may be introduced
in a future version, but as an alternative the DOM models in use within the
classes are publicly accessible, allowing the package to be wrapped with
special handlers.

For example, to make use of the 'pheed' extension (namespace
http://www.pheed.com/pheed/) we might use: